Getting an invalid response with new line symbol at the response on SAM CLI 0.4.0

[makskant]

Description:

Steps to reproduce the issue:

1. Function handler

def handler(event, context):
    return {'body': json.dumps([]), 'statusCode': 200, 'headers': {"Cache-Control":"max-age=1200"}}

2. Resource

    TestFunction:
        Type: AWS::Serverless::Function
        Properties:
            Handler: test.handler
            Role: !GetAtt FunctionRole.Arn
            CodeUri: functions/
            AutoPublishAlias: live
            Events:
                Api:
                    Type: Api
                    Properties:
                        Path: /test
                        Method: get

3. Running sam local start-api and trying to requests a http://127.0.0.1:3000/test

Observed result:

Function returned an invalid response (must include one of: body, headers or statusCode in the response object). Response received: b'\n{"body": "[]", "statusCode": 200, "headers": {"Cache-Control": "max-age=1200"}}'

Expected result:
Expecting to have an empty array as a response with status code 200

OS: Ubuntu 16.04

Output of sam --version: 0.4.0

Python version: 3.6.1.

Optional Debug logs:

START RequestId: 90197d0b-c013-4575-bbe0-2eb8c3d67714 Version: $LATEST
END RequestId: 90197d0b-c013-4575-bbe0-2eb8c3d67714
REPORT RequestId: 90197d0b-c013-4575-bbe0-2eb8c3d67714 Duration: 339 ms Billed Duration: 400 ms Memory Size: 128 MB Max Memory Used: 29 MB
2018-07-05 16:52:11 http://localhost:None "GET /v1.35/containers/db47404069e7220f7ee521898dad6f27131a5e8f8b6d2b0a6d035aa3ffd9097e/json HTTP/1.1" 200 None
2018-07-05 16:52:11 http://localhost:None "DELETE /v1.35/containers/db47404069e7220f7ee521898dad6f27131a5e8f8b6d2b0a6d035aa3ffd9097e?force=True&v=False&link=False HTTP/1.1" 204 0
2018-07-05 16:52:11 Function returned an invalid response (must include one of: body, headers or statusCode in the response object). Response received: b'\n{"body": "[]", "statusCode": 200, "headers": {"Cache-Control": "max-age=1200"}}'
2018-07-05 16:52:11 127.0.0.1 - - [05/Jul/2018 16:52:11] "GET /test HTTP/1.1" 502 -
2018-07-05 16:52:11 127.0.0.1 - - [05/Jul/2018 16:52:11] "GET /favicon.ico HTTP/1.1" 403 -

[jfuss]

hmmm... Something is going wrong in this function but at first glance I can't reason about what the actually issue is. I will need to run the cli with pdb with your template and code.

Note: Thank you for providing the code and template. This makes tracking this down much easier!

[zsc347]

I've found a fix.
This line should be

if last_line_position >= 0:

And there is another error which will cause decode exception.
This line shoud be

json_output = json.loads(lambda_output.decode('utf-8'))

[sanathkr]

@zsc347 Can you send a PR to fix the >=0 bug along with a unit tests? Should be super easy.

For the second one, @jfuss is working on this code path in #532. I have made a note of this comment there. He should be able to handle it.

[jfuss]

Acknowledging I will handle the second one @zsc347 provided in my current PR @sanathkr linked.

[jfuss]

Both bugs called out here were addressed with released v0.5.0

Closing as this is released